/*
 * Copyright 2001 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.nio.cs;

import java.nio.*;
import java.nio.charset.*;

/**
 * Utility class for caching per-thread decoders and encoders.
 */

public class ThreadLocalCoders {

	private static final int CACHE_SIZE = 3;

	private static abstract class Cache {

		// Thread-local reference to array of cached objects, in LRU order
		private ThreadLocal cache = new ThreadLocal();
		private final int size;

		Cache(int size) {
			this.size = size;
		}

		abstract Object create(Object name);

		private void moveToFront(Object[] oa, int i) {
			Object ob = oa[i];
			for (int j = i; j > 0; j--)
				oa[j] = oa[j - 1];
			oa[0] = ob;
		}

		abstract boolean hasName(Object ob, Object name);

		Object forName(Object name) {
			Object[] oa = (Object[]) cache.get();
			if (oa == null) {
				oa = new Object[size];
				cache.set(oa);
			} else {
				for (int i = 0; i < oa.length; i++) {
					Object ob = oa[i];
					if (ob == null)
						continue;
					if (hasName(ob, name)) {
						if (i > 0)
							moveToFront(oa, i);
						return ob;
					}
				}
			}

			// Create a new object
			Object ob = create(name);
			oa[oa.length - 1] = ob;
			moveToFront(oa, oa.length - 1);
			return ob;
		}

	}

	private static Cache decoderCache = new Cache(CACHE_SIZE) {
		boolean hasName(Object ob, Object name) {
			if (name instanceof String)
				return (((CharsetDecoder) ob).charset().name().equals(name));
			if (name instanceof Charset)
				return ((CharsetDecoder) ob).charset().equals(name);
			return false;
		}

		Object create(Object name) {
			if (name instanceof String)
				return Charset.forName((String) name).newDecoder();
			if (name instanceof Charset)
				return ((Charset) name).newDecoder();
			assert false;
			return null;
		}
	};

	public static CharsetDecoder decoderFor(Object name) {
		CharsetDecoder cd = (CharsetDecoder) decoderCache.forName(name);
		cd.reset();
		return cd;
	}

	private static Cache encoderCache = new Cache(CACHE_SIZE) {
		boolean hasName(Object ob, Object name) {
			if (name instanceof String)
				return (((CharsetEncoder) ob).charset().name().equals(name));
			if (name instanceof Charset)
				return ((CharsetEncoder) ob).charset().equals(name);
			return false;
		}

		Object create(Object name) {
			if (name instanceof String)
				return Charset.forName((String) name).newEncoder();
			if (name instanceof Charset)
				return ((Charset) name).newEncoder();
			assert false;
			return null;
		}
	};

	public static CharsetEncoder encoderFor(Object name) {
		CharsetEncoder ce = (CharsetEncoder) encoderCache.forName(name);
		ce.reset();
		return ce;
	}

}